Method:Preheat the oven to 325 F.
Boil unpeeled potatoes with bay leaves and peppercorns. Drain, peel while still hot, and rice or push through a sieve. Let cool slightly and add egg yolk. Mix well. Add lemon juice and cream. Season with salt and pepper and whip with a beater until smooth. Keep warm.
Saute mushrooms and onions in butter until all the liquid has evaporated. Combine with crab meat, Bechamel sauce, and brandy. Season with salt and pepper.
Divide the crab mixture among the ramekins and even out the top. Next, divide the potato mixture among the ramekins. Do not mix the two layers.
Sprinkle lightly with Parmesan and bake until heated through and bubbly, about 35 minutes.
Remove from the oven, let cool slightly, dust with cayenne pepper, and top each ramekin with a small lump of caviar (if using).